The present invention relates to a control device for a car-mounted air conditioner.
In the conventional, car-mounted air-conditioner, the room or passenger compartment temperature of a car is controlled by changing the temperature of air blown into the room by directing a portion of the cold air obtained from an evaporator through an air-mixing damper of the vacuum type and passing the portion through a heater. A typical example of such a conventional control device is shown in FIG. 1, in which outputs of a temperature setting device 01 and of a room temperature sensor 02, both of which are mounted on the car, are supplied to a temperature controller 03 where a deviation of the actual temperature from a previously set temperature is obtained. The output of the temperature controller 03 is fed to a double vacuum valve device 04, which is also controlled by a vacuum tank 06 through a check valve 05, to drive a power servo 07 for rotating an air mixing damper 09. The rotation of the damper 09 is fed back through a potentiometer 08 to the temperature controller 03.
The car-mounted air-conditioner of this type is now widely used successfully. It has some inherent defects, however, such as the need for providing a vacuum source and many constitutional components for driving the vacuum source, which cause the system to be expensive and to require a larger spacing for the piping of the vacuum source, and the low resolution of the air mixing damper positioning, i.e., the unavoidable hysteresis in the reciprocation of the damper.